A long-term sexual relationship before conception makes for a healthier pregnancy

You can add sex to your list of things to do for a healthier pregnancy — but you'll have to start long before you start trying to conceive.

According to research and clinical studies by Robinson Research Institute and University of Adelaide, women who have regular sex with the same partner for at least three months before conception have less risk of developing preeclampsia, a potentially serious condition for both the mother and the baby.

"'Preeclampsia is more common when there has been limited sexual contact with the father before pregnancy is conceived and is associated with insufficient establishment of immune tolerance in the mother," said Professor Sarah Robertson from the University of Adelaide.

It all comes down to timing, it seems. "Women with less than three months sexual activity with the conceiving partner had a 13 per cent chance of preeclampsia, more than double the average occurrence," Robertson explained.

The chance of preeclampsia was 22 percent for women who conceived on the first sexual contact with the father, which is three times higher than the average. In this group, low birth weight babies were also more common.

Sex is also an important factor for couples going through IVF, with a study of Australian and Spanish couples showing that sex in the days immediately before or after embryo transfer boosted pregnancy rates by 50 percent.

So why does long-term sex with the same partner help facilitate a healthy pregnancy? Without getting too scientific, it all comes down to the relationship between the man's seminal fluid and the woman's immune system. Over time, repeated contact with the same male partner helps build up a tolerant immune response (recognising and accepting his swimmers, you might say.)

Note that it's the duration of sexual relationship and not the frequency of sexual intercourse that's important. "No relationship is observed between frequency of sexual activity during pregnancy and risk for preeclampsia," said Robertson.